The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An airplane is driven by several turbine engines each accommodated in a nacelle used for channeling the airflows generated by the turbine engine which also harbors a set of ancillary actuation devices related to its operations and ensuring diverse functions when the turbine engine is operating or at a standstill.
These ancillary actuation devices notably comprise a mechanical system for thrust reversal and a variable nozzle system.
A nacelle generally has a tubular structure comprising an air intake upstream from the turbine engine, a middle section intended to surround a fan of the turbine engine, a downstream section harboring thrust reversal means and intended to surround the combustion chamber of the turbine engine, and it is generally completed with an ejection nozzle, the outlet of which is located downstream from the turbine engine.
Modern nacelles are intended to harbor a dual flow turbine engine capable of generating via the rotating blades of the fan a flow of hot air (also called primary flow) from the combustion chamber of the turbine engine, and a cold air flow (secondary flow) which circulates outside the turbine engine through an annular passage, also called a vein, formed between a fairing of the turbine engine and an internal wall of the nacelle. Both air flows are ejected from the turbine engine through the rear of the nacelle.
The role of a thrust reverser during the landing of an airplane is to improve the braking capability of the latter by redirecting forwards at least one portion of the thrust generated by the turbine engine. In this phase, the reverser shuts off the vein of the cold flow and directs the latter towards the front of the nacelle, thereby generating a counter thrust which will be added to the braking of the wheels of the airplane.
The means applied for achieving this reorientation of the cold flow vary according to the reverser type. However, in all cases, the structure of a reverser comprises movable cowls which may be displaced between a deployed position in which they open in the nacelle a passage intended for the deflected flow on the one hand, and a retracted position in which they close this passage on the other hand. These cowls may fulfill a deflection function or a function simply for activating other deflection means.
In the case of a reverser with grids, also known as a cascade reverser, the reorientation of the air flow is carried out by deflection grids, the cowl only having a simple sliding function aiming at uncovering or covering these grids, the translation of the movable cowl being carried out along a longitudinal axis substantially parallel to the axis of the nacelle. Additional blocking gates, activated by the sliding of the cowling, generally allows the vein to be closed downstream from the grids so as to optimize the reorientation of the cold flow.
In addition to its thrust reversal function, the sliding cowl belongs to the rear section and has a downstream side forming an ejection nozzle aiming at channeling the ejection of the air flows. This nozzle may be an addition to a primary nozzle channeling the hot flow and is then called a secondary nozzle.
The performances of thrust reversal are satisfactorily obtained with the known devices. However, for reasons of aerodynamic optimization, and consequently optimization of fuel consumption, it is quite advantageous to be able to adjust the section of the outlet for the cold air flow downstream from the nacelle: it is indeed useful to be able to increase this section during take-off and landing phases, and to reduce it during cruising phases: this is often referred to as an adaptive nozzle, or else further as a “VFN” (Variable Fan Nozzle).
Such a system is described in document FR 2 622 929 or further FR 2 902 839 for example.
These documents describe the application of thrust reversers with grids, equipped with a variable ejection section and to do this provides a movable cowl comprising two portions which may be connected together with locking means.
According to the embodiments, the variable nozzle may be made from one or several dedicated movable elements, such as pivoting flaps or a translatable cowl portion or this function may be fulfilled by the movable cowl itself by low amplitude translational movements not activating the thrust reversal function.
For an extensive and detailed description of different embodiments, reference may be made to documents FR 2 922 058, FR 2 902 839, FR 2 922 059, inter alia.
The operating phases of the variable nozzle and of the thrust reverser are distinct. The variable nozzle can only operate when the reverser is actuated upon landing. Vice versa, the thrust reverser should not operate when the variable nozzle section is maneuvering.
Moreover, the adaptive nozzle is located in the downstream extension of the thrust reversal cowl, and it is important to be able to actuate both of these portions of the nacelle independently; in particular the intention is to be able to increase the section of the adaptive nozzle without actuating the thrust reversal means, in particular during take-off.
In order to achieve this independent actuation, each movable portion (reverser/nozzle) may conventionally be equipped with its own actuator (two single rod actuators or a dual rod actuator cylinder, for example) and be driven independently.
In order to make the driving assembly lighter, it is possible to use a simple single-rod actuator, by providing additional locking means between the movable portions.
Such a solution and a few application principles are shown in document FR 2 902 839, notably in FIGS. 13 to 15.